feat: API_REFERENCE.md doc and generation script

[mbarlow12]

Adds:

• A minimal document for the endpoints & request/response shapes.
• Script to check that the doc is up to date & for generating the minimal doc content
  • Lot's of room for improvement here (e.g. incremental updates, retaining handwritten content, more detailed request/response schemas, etc...)

Usage
Check that endpoints are in sync:

# from repo root
./deployments/api/scripts/api_doc.py check [optional path to doc]

Generate the new doc skeleton to stdout:

./deployments/api/scripts/api_doc.py gen

# write to a file
./deployments/api/scripts/api_doc.py gen -o ./deployments/api/API_REFERENCE_updated.md

# create a "new" file, outputs `API_REFERENCE_[timestamp].md`
./deployments/api/scripts/api_doc.py gen --new

This is the quick & dirty to allow more incremental updates and so we can retain hand-written changes to API_REFERENCE.md. Example workflow: run check (get error), run gen --new, copy the new section to API_REFERENCE.md.